Leishmanial isolates from patients continue to provide a rich source of material for experimental studies. The suceptible BALB/c mouse is proving especially useful in classification of leishmanial species. Four isolates of L. tropica minor, for example, exhibit long persistence at the site of inoculation in BALB/c footpads without producing a lesion. The sequential development of lesions with different leishmanial parasites causing cutaneous disease is being studied in the ears of BALB/c mice. A technique that permits accurate localization to the injection site is utilized. Earliest histologic changes are seen within 24-48 hours after inoculation. Five patients with the unusual anergic form of diffuse cutaneous leishmaniasis (DCL) were studied in Ethiopia. Local heat therapy failed to eliminate parasites from skin lesions of three of the patients who were tested. Lymphocytes from the DCL patients were unreponsive to leishmanial antigens in vitro, even after addition of exogenous IL-2.